Plack - LPW 2009

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PSGI and Plack
Tatsuhiko Miyagawa
London Perl Workshop 2009

Tatsuhiko Miyagawa

• Japanese, lives in San Francisco
• Works at Six Apart
• 170+ CPAN modules (id:MIYAGAWA)
• @miyagawa
...

Background

Web Frameworks

Maypole Mason Mojo Sledge Catalyst Spoon PageKit
AxKit Egg Gantry Continuity Solstice Mojolicious
Tripletail Konstrukt Re...

Most of them run on
mod_perl and CGI

Some run on FastCGI

Some run standalone

Very few supports
non-blocking

Because:

No common server
environment layers

CGI.pm

Runs “ﬁne” on:
CGI, FastCGI, mod_perl (1 & 2)
Standalone (with HTTP::Server::Simple)

CGI.pm = LCD
It’s also Perl core

Catalyst
The most popular framework as of today

Catalyst::Engine::*
Server abstractions.
Well supported Apache, FCGI and Standalone
No CGI.pm

CGI.pm
Jifty, CGI::Application, Spoon

mod_perl centric
Mason, Sledge, PageKit, WebGUI

Adapters
Catalyst, Ma...

Problems:
Duplicated efforts
No fair performance evaluations

Question:
Can we share
those adapters?

Answer:
HTTP::Engine

HTTP::Engine
Lots of adapters (FCGI, Apache2, POE)
Clean Request/Response API
Written by Yappo, tokuhirom and others

Problems

Mo[ou]se everywhere
Mouse is light but still overspec for some env.

Monolithic
All implementations share HTTP::Engine roles
and builders, which is sometimes hard to adapt
and has less ...

APIs everywhere
Most frameworks have their request/response API
Sometimes there are gaps.
Annoying to write ...

Solution

Steal good stuff
from Python/Ruby

WSGI (Python)
Rack

WSGI (PEP-333)
mod_wsgi, Paste, AppEngine
Django, CherryPy, Pylons

Rack
Passenger, thin, Unicorn, Heroku
Rails, Merb, Sinatra

WSGI/Rack
Completely separate interface
from the actual implementation

Approach
Split HTTP::Engine
into three parts

Interface
Implementations
Utilities

PSGI (interface)
Plack::Server (implementations)
Plack::* (utilities)

Who’s on board
Benjamin Trott, Yuval Kogman, Stevan Little, Shawn M
Moore, Mark Stosberg, Matt S Trout, Jesse Vincent,
...

PSGI
Perl Web Server Gateway Interface

Interface

WARNING
You DON’T need to care about these
interface details as an app developer.

my $app = sub {
my $env = shift;
# ...
return [ $status, $header, $body ];
};

PSGI application
code reference
$app = sub {...};

my $app = sub {
my $env = shift;
# ...
return [ $status, $header, $body ];
};

environment hash
$env: CGI-like env variables
+ psgi.input, psgi.errors etc.

my $app = sub {
my $env = shift;
# ...
return [ $status, $header, $body ];
};

Response
array ref with three elements
status code, headers (array ref)
and body (IO-like or array ref)

my $app = sub {
my $env = shift;
# ...
return [ $status, $header, $body ];
};

$body
IO::Handle-like
getline() and close()

IO::Handle-like
We really envy Python/Ruby
for built-in iterators
(Perl’s ﬁlehandle is also an object, bu...

WARNING
You DON’T need to care about these
interface details as an app developer.
Becuase ...

Frameworks
Write an adapter to return
PSGI application code ref.
(and forget about servers!)

Framework Adapters
CGI::Application, Catalyst, Maypole
Mason, Squatting, Mojo, HTTP::Engine etc.

Applications
MT::App, WebGUI

$use Foo; # is a Catalyst application Foo->setup_engine(‘PSGI’); my $app = sub { Foo->run };$

Servers
Set up $env, run the app
and emits response out of $res

Plack
namespace for servers and utilities

Plack::Server
reference server implementations
Standalone, FCGI, Apache2, CGI
Standalone, Prefork, AnyEvent, Coro

Very fast
5000 QPS on standalone
15000 QPS with prefork :)

Utilities

Plackup
Run PSGI app instantly from CLI
(inspired by rackup)

DEMO

Middleware

my $app = sub {
my $env = shift;
return [ $status, $header, $body ];
};

my $mw = sub {
my $env = shift;
# do ...

Middleware
Static, AccessLog, ConditionalGET
ErrorDocument, StackTrace etc.

Plack::Middleware
reusable and extensible
Middleware framework
Plack::Builder DSL in .psgi

my $app = sub {
return [ $status, $header, $body ];
};

use Plack::Builder;

builder {
enable “Static”, root => “/htd...

Plack::App::URLMap
Multiplex multiple apps
Integrated with Builder DSL

$use CatApp; use CGIApp; my $c1 = sub { CatApp->run }; my $c2 = sub { CGIApp->run_psgi }; use Plack::Builder; builder { ...$

CGI::PSGI
Easy migration from CGI.pm

CGI::Emulate::PSGI
CGI::Compile
Easiest migration from CGI scripts (like Registry)

Plack::Request
like libapreq (Apache::Request)
wrapper APIs for framework developers

use Plack::Request;

my $app = sub {
my $req = Plack::Request->new(shift);

my $body = “Hello “ . $req->param(‘n’);
my ...

Plack::Test
Uniﬁed interface to write tests
with Mock HTTP and Live HTTP

use Plack::Test;
use HTTP::Request::Common;

my $app = sub {
my $env = shift;
return [ $status, $header, $body ];
};...

use Plack::Test;
use HTTP::Request::Common;
$Plack::Test::Impl = “Server”;

my $app = sub {
my $env = shift;
return ...

Streaming
event loop / long-poll

$# Pull streaming for blocking server use IO::Handle::Util qw(io_from_getline); my $app = sub { my $env = shift; my ...$

# Push streaming for non-blocking server
use AnyEvent;
use JSON;

my $app = sub {
my $env = shift;
return sub {
my...

Non-blocking servers
AnyEvent, Coro, POE, Danga::Socket

Non-blocking framework
Tatsumaki
http://github.com/miyagawa/Tatsumaki

Other Servers

nginx embedded perl
http://github.com/yappo/nginx-psgi-patchs

mod_psgi
http://github.com/spiritloose/mod_psgi

evpsgi
http://github.com/sekimura/evpsgi

Perlbal plugin
http://github.com/miyagawa/Perlbal-Plugin-PSGI

Cloud

WSGI (PEP-333)
mod_wsgi, Paste, AppEngine
Django, CherryPy, Pylons

Rack
Passenger, Thin, Unicorn, Heroku
Rails, Merb, Sinatra

What if GAE Perl
comes with PSGI ...

Summary

• PSGI is an interface, Plack is the code.
• We have many (pretty fast) servers.
• We have adapters and tools for...

http://github.com/miyagawa/Plack
http://plackperl.org/
http://advent.plackperl.org/ ←NEW!
irc://irc.perl...

Questions?